Bearing assemblies including thick superhard tables and/or selected exposures, bearing apparatuses, and methods of use

ABSTRACT

Embodiments of the invention are directed to bearing assemblies configured to effectively provide heat dissipation for bearing elements, bearing apparatuses including such bearing assemblies, and methods of operating such bearing assemblies and apparatuses. In an embodiment, a bearing assembly includes a plurality of superhard bearing elements distributed about an axis. Each superhard bearing element of the plurality of superhard bearing elements has a superhard table including a superhard surface. The bearing assembly includes a support ring structure coupled to the plurality of superhard bearing elements. One or more of the superhard bearing elements includes a superhard table, which may improve heat transfer from such superhard bearing elements.

BACKGROUND

Subterranean drilling systems that employ downhole drilling motors arecommonly used for drilling boreholes in the earth for oil and gasexploration and production. A subterranean drilling system typicallyincludes a downhole drilling motor that is operably connected to anoutput shaft. Bearing apparatuses (e.g., thrust, radial, tapered, andother types of bearings) also may be operably coupled to the downholedrilling motor. A rotary drill bit configured to engage a subterraneanformation and drill a borehole is connected to the output shaft. As theborehole is drilled with the rotary drill bit, pipe sections may beconnected to the subterranean drilling system to form a drill stringcapable of progressively drilling the borehole to a greater depth withinthe earth.

A typical bearing apparatus includes a stator that does not rotate and arotor that is attached to the output shaft and rotates with the outputshaft. The stator and rotor each includes a plurality of bearingelements, which may be fabricated from polycrystalline diamond compacts(“PDCs”) that provide diamond bearing surfaces that bear against eachother during use.

The operational lifetime of the bearing apparatuses often determines theuseful life of the subterranean drilling system. Therefore,manufacturers and users of subterranean drilling systems continue toseek improved bearing apparatuses to extend the useful life of suchbearing apparatuses.

SUMMARY

Embodiments of the invention are directed to bearing assembliesconfigured to effectively provide heat dissipation for bearing elements,bearing apparatuses including such bearing assemblies, and methods ofoperating such bearing assemblies and apparatuses. In an embodiment, abearing assembly includes a plurality of superhard bearing elementsdistributed about an axis. Each superhard bearing element of theplurality of superhard bearing elements has a superhard table includinga superhard surface. The bearing assembly includes a support ringstructure coupled to the plurality of superhard bearing elements. One ormore of the superhard bearing elements includes a superhard table, whichmay improve heat transfer from such superhard bearing elements.

In an embodiment, a bearing assembly includes a first plurality ofsuperhard bearing elements distributed about an axis. Each of the firstplurality of superhard bearing elements has a superhard materialincluding a superhard bearing surface. The bearing assembly alsoincludes a support ring structure coupled to the first plurality ofsuperhard bearing elements. Additionally, the superhard material of atleast some of the first plurality of superhard bearing elements has amaximum thickness that is at least 0.120″.

In one or more embodiments, a bearing apparatus includes a first bearingassembly, which includes one or more first bearing surfaces and a firstsupport ring structure that includes the one or more first bearingsurfaces. The bearing assembly also includes a second bearing assembly,which includes a second plurality of superhard bearing elements. Each ofthe second plurality of superhard bearing elements including superhardmaterial having a second superhard bearing surface positioned andoriented to slidingly engage the one or more first bearing surfaces ofthe first bearing assembly. The second bearing assembly also includes asecond support ring structure that carries the second plurality ofsuperhard bearing elements. In addition, the superhard material of atleast some of the second plurality of superhard bearing elements has athickness that is at least 0.120″.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments, wherein identical referencenumerals refer to identical or similar elements or features in differentviews or embodiments shown in the drawings.

FIG. 1A is a cross-sectional view of a thrust-bearing assembly accordingto an embodiment;

FIG. 1B is a cross-sectional view of a thrust-bearing assembly accordingto another embodiment;

FIG. 1C is a cross-sectional view of a thrust-bearing assembly accordingto yet one other embodiment;

FIG. 1D is a cross-sectional view of an embodiment of a thrust-bearingassembly that has more exposure of superhard bearing elements on anouter side of a support ring structure than on an inner side thereof;

FIG. 2A is an isometric view of a bearing element according to anembodiment;

FIG. 2B is a cross-sectional view of a bearing element according to anembodiment;

FIG. 2C is a cross-sectional view of a bearing element according toanother embodiment;

FIG. 2D is a cross-sectional view of a bearing element according to yetone other embodiment;

FIG. 2E is a cross-sectional view of a bearing element according to anembodiment;

FIG. 2F is a cross-sectional view of a bearing element according tostill another embodiment;

FIG. 3 is an isometric view of a thrust-bearing apparatus according toan embodiment, which may employ one or more of the thrust-bearingassembly embodiments disclosed herein;

FIG. 4A is a cross-sectional view of a first radial-bearing assemblyaccording to an embodiment;

FIG. 4B is a cross-sectional view of a first radial-bearing assemblyaccording to another embodiment;

FIG. 4C is a cross-sectional view of a first radial-bearing assemblyaccording to yet another embodiment;

FIG. 4D is a cross-sectional view of a second radial-bearing assemblyaccording to an embodiment;

FIG. 5 is an isometric view of a radial-bearing apparatus according toan embodiment, which may employ any of the radial bearing assemblyembodiments disclosed herein; and

FIG. 6 is an isometric view of a subterranean drilling system accordingto an embodiment, which may employ any of the thrust-bearing and/orradial bearing apparatus embodiments disclosed herein.

DETAILED DESCRIPTION

Embodiments of the invention are directed to bearing assembliesconfigured to effectively provide heat dissipation for bearing elements,bearing apparatuses including such bearing assemblies, and methods ofoperating such bearing assemblies and apparatuses. In particular, one ormore embodiments include a bearing apparatus, which may include firstand second bearing assemblies (e.g., a stator and a rotor) configured toengage one another, and any of which may provide heat dissipation fromthe bearing elements that may comprise the first and/or second bearingassemblies.

For instance, some or all of the bearing elements of the first and/orsecond bearing assemblies may be superhard bearing elements. As usedherein, a “superhard bearing element” is a bearing element including abearing surface that is made from a material exhibiting a hardness thatis at least as hard as tungsten carbide. In any of the embodimentsdisclosed herein, the superhard bearing elements may include one or moresuperhard materials, such as polycrystalline diamond, polycrystallinecubic boron nitride, silicon carbide, tungsten carbide, or anycombination of the foregoing superhard materials. In an embodiment, thesuperhard bearing elements may include a superhard table, which may behighly thermally conductive. Furthermore, in some instances, thesuperhard table may be a superhard table, which may provide increasedtransfer of heat from the superhard bearing elements (as compared with astandard superhard table). Specifically, such superhard bearing elementsmay have increased surface areas that may be exposed to a coolingmedium, such as drilling fluid, coolant, air, etc., which may facilitateefficient convective heat transfer from the bearing elements.

It should be appreciated that, typically, a manufacturer may prefer tolimit the thickness of the superhard table (e.g., to about less than0.080″). For instance, increased thickness of the superhard table, suchas polycrystalline diamond compact table, may increase manufacturingcosts. According to principals of this disclosure, however, as describedfurther below, superhard table of the bearing elements may increaseuseful life/performance of the bearing assemblies and/or of the bearingapparatus, by facilitating efficient heat dissipation. Furthermore, suchsuperhard tables of the bearing elements may increase a maximum loadthat the bearing assemblies and apparatuses (e.g., by increasingconvective heat transfer from the bearing elements and preventingoverheating thereof) can experience during use without failure.

Limiting protruding portions of the bearing elements in the standardbearing assembly may be aimed at reducing moment and/or shear forcesexperienced by such bearing elements. To provide sufficient exposure tothe cooling medium, in an embodiment, the bearing elements describedherein may protrude from the support ring structure in excess to bearingelements associated as compared with the standard bearing elementsand/or bearing assemblies. In addition to or in lieu of over-protruding,the bearing elements may include the superhard table, which may improveor increase heat transfer from the bearing elements, as compared withthe bearing elements of the typical bearing assembly. According to thepresent disclosure, any negative effects to performance of the bearingdue to increased forces that may be experienced by the bearing elements(i.e., forces applied to bearing surfaces) may be compensated for byincreased efficiency in transferring heat from the bearing elements.Moreover, under some operating conditions, increased heat transferefficiency may lead to increased load bearing capacity of the bearingassemblies and apparatuses.

Heating of the bearing elements above a certain temperature may degradeor damage the superhard material of the superhard table of the bearingelements. Under some operational conditions, increased load on thebearing apparatus, on the bearing assembly, and/or on particular bearingelements may lead to a corresponding increase in temperature. In anembodiment, any of the configuration, design, position, or combinationsthereof of the superhard table and/or of the bearing elements mayprevent the temperature from increasing to or above a detrimentaltemperature that may damage or degrade the superhard table.Particularly, as noted above, the superhard table of such bearingelements may facilitate sufficient cooling of the superhard table by thecooling medium, which may reduce increases in temperature of thesuperhard table during use.

Also, in some operational conditions, one or more of the bearingelements may be preferentially loaded, such as to carry preferentiallyhigher loads (e.g., radial and/or axial loads). The bearing elementsexperiencing higher loads also may experience a higher thermal load ormay heat up at an accelerated rate, as compared with other bearingelements. Hence, an embodiment optionally includes bearing assembliesand/or bearing apparatuses that include higher loaded bearing elementsthat incorporate a superhard table. Furthermore, the higher loadedbearing elements may optionally be over-protruding relative to a supportring structure of the bearing assembly. Thus, in some embodiments, thesuperhard table thickness and/or protrusion of higher loaded bearingelements may be selected, alone or in combination, to maintain a desiredoperating temperature of the higher loaded bearing elements during use.

Also, accelerated and/or uneven heating or thermal loading of thebearing elements may lead to premature failure of the bearing assembly.For instance, thermal expansion of the high-load bearing elements mayfurther increase forces and/or friction experienced by one or more ofsuch bearing elements. In some instances, increased force on the bearingelements may lead to deformation and/or fracturing of the bearingassembly and/or component or elements thereof. In any case, acceleratedand/or uneven heating of the bearing elements may prematurely causedamage thereto (e.g., by damaging or degrading the superhard materialthat may comprise such bearing elements), which may lead to the failureof the bearing assembly. Accordingly, enhanced cooling of the higherloaded bearing elements may limit or prevent premature failure of thebearing assembly.

In some instances, the bearing assembly may receive and/or generate moreheat in or near a first portion thereof (e.g., a portion under a higherload), which may increase the temperature in the first portion of thebearing assembly, while the temperature in a second portion of thebearing assembly may remain at a lower temperature. Such uneventemperature distribution may warp the bearing assembly. Furthermore, insome situations, warping may inhibit or prevent hydrodynamic operationof the bearing apparatus and/or may unevenly load the bearing elements.In an embodiment, over-protruding bearing elements and/or bearingelements with superhard table may be positioned in or near the firstportion of the bearing assembly to provide enhanced heat dissipation atthe first portion of the bearing assembly, which may extend useful lifeof the bearing assembly.

FIG. 1A illustrates a thrust-bearing assembly 100 a according to anembodiment. The thrust-bearing assembly 100 a may include a support ringstructure 110 a that carries superhard bearing elements 120 a. Thesupport ring structure 110 a may form or define the opening 130 therein.In some embodiments, the opening 130 may have a substantially circularor cylindrical shape. Alternatively, the opening 130 may have any numberof suitable shapes, which may vary from one embodiment to another. Inany case, the opening 130 may accommodate a shaft or other machinecomponent or element that may pass therethrough and/or may be securedthereto. Furthermore, in an embodiment, the support ring structure 110 amay have no opening.

Additionally, the support ring structure 110 a may form or define anouter perimeter of the thrust-bearing assembly support ring structure110 a. Similar to the opening 130, the outer perimeter formed by thesupport ring structure 110 a also may have any number of suitableshapes. In an embodiment, the outer perimeter has a substantiallycircular shape. In other embodiments, however, the outer perimeter mayhave a rectangular, triangular, trapezoidal, or essentially any othershape.

In an embodiment, the support ring structure 110 a may include a supportring 140 a that may secure and support the superhard bearing elements120 a. The superhard bearing elements 120 a may be secured to thesupport ring structure 110 a in any number of suitable ways that mayvary from one embodiment to the next. For instance, the superhardbearing elements 120 a may be at least partially secured within recesses141 a via brazing, press-fitting, threadedly attaching, fastening with afastener, combinations of the foregoing, or another suitable technique.The recesses 141 a may be located in and/or defined by the support ring140 a.

The superhard bearing elements 120 a may have any number of suitablearrangements on the support ring structure 110 a, which may vary fromone embodiment to another. For example, the superhard bearing elements120 a may be circumferentially positioned about a thrust axis 10 a onthe support ring structure 110 a. Moreover, the superhard bearingelements 120 a may be arranged in a single row about the support ringstructure 110 a. In additional or alternative embodiments, the superhardbearing elements 120 a may be distributed in two rows, three rows, fourrows, or any other number of rows.

The support ring 140 a may include a variety of different materials orcombinations of materials. For example, the support ring 140 a mayinclude a metal, alloy steel, a metal alloy, carbon steel, stainlesssteel, tungsten carbide, or combinations thereof. As further describedbelow, various portions of the support ring structure 110 a (e.g., thesupport ring 140 a) may include any number of other suitable orconductive, non-conductive, or semiconductive materials. In any event,the support ring 140 a may include a suitable material, havingsufficient strength and resilience to support the superhard bearingelements 120 a.

In additional or alternative embodiments, the support ring structure 110a may include multiple elements or components coupled or securedtogether. For instance, the support ring structure may include a supportring and a retaining ring coupled to the support ring. Such retainingring may include counterbored or countersunk openings that mayfacilitate securing the bearing elements to the support ring structure.For example, in one embodiment, the bearing elements may include ashoulder that may interface with the counterbore or countersink of theopenings in the retaining ring of the support ring structure, which mayallow the retaining ring to secure the bearing elements to the supportring. In turn, the retaining ring may be fastened (e.g., bolted,screwed, etc.), welded, brazed, or otherwise secured to the supportring. In any event, the support ring structure 110 a may secure, as wellas provide sufficient support, to the superhard bearing elements 120 a.Embodiments of support ring structures including a retaining ringcoupled to a support ring to retain superhard bearing elements aredisclosed in U.S. Pat. No. 7,870,913 and U.S. application Ser. No.12/761,535, the disclosures of both of which are incorporated herein, intheir entirety, by this reference.

The superhard bearing elements 120 a may include one or more surfacesthat form a peripheral surface 121 a of the superhard bearing elements120 a. Generally, the shape of the peripheral surface 121 a and/or sizeof the superhard bearing elements 120 a may vary from one embodiment toanother. For example, the superhard bearing elements 120 a may have asubstantially cylindrical peripheral surface 121 a. In one or moreembodiments, the superhard bearing elements 120 a may have a cuboid,conical, prismoid, complex peripheral surfaces, or any desired shape.

In one or more embodiments, the superhard bearing elements 120 a may bepre-machined to selected tolerances and mounted in the support ringstructure 110 a. Optionally, the superhard bearing elements 120 a may befirst mounted in the support ring structure 110 a and then planarized(e.g., by grinding and/or lapping) to form bearing surfaces 122 athereof, so that the bearing surfaces 122 a are substantially coplanar.Optionally, one or more of the superhard bearing elements 120 a may havea peripherally extending edge chamfer.

In some embodiments, the superhard bearing elements 120 a may include asuperhard table 150 a bonded to a substrate 160 a. For example, thesuperhard table 150 a may comprise polycrystalline diamond and thesubstrate 160 a may comprise cobalt-cemented tungsten carbide. Othercarbide materials may be used with tungsten carbide or as analternative, such as chromium carbide, tantalum carbide, vanadiumcarbide, titanium carbide, or combinations thereof cemented with iron,nickel, cobalt, or alloys thereof. Furthermore, in any of theembodiments disclosed herein, the polycrystalline diamond table may beleached to at least partially remove or substantially completely removea metal-solvent catalyst (e.g., cobalt, iron, nickel, or alloys thereof)that was used to initially sinter precursor diamond particles to formthe polycrystalline diamond. In another embodiment, an infiltrant usedto re-infiltrate a preformed leached polycrystalline diamond table maybe leached or otherwise removed to a selected depth from a bearingsurface. Moreover, in any of the embodiments disclosed herein, thepolycrystalline diamond may be un-leached and include a metal-solventcatalyst (e.g., cobalt, iron, nickel, or alloys thereof) that was usedto initially sinter the precursor diamond particles that form thepolycrystalline diamond and/or an infiltrant used to re-infiltrate apreformed leached polycrystalline diamond table. Examples of methods forfabricating the superhard bearing elements and superhard materialsand/or structures from which the superhard bearing elements may be madeare disclosed in U.S. Pat. Nos. 7,866,418; 7,998,573; 8,034,136; and8,236,074; the disclosure of each of the foregoing patents isincorporated herein, in its entirety, by this reference.

The diamond particles that may be used to fabricate the superhard table150 a in a high-pressure/high-temperature process (“HPHT)” may exhibit alarger size and at least one relatively smaller size. As used herein,the phrases “relatively larger” and “relatively smaller” refer toparticle sizes (by any suitable method) that differ by at least a factorof two (e.g., 30 μm and 15 μm). According to various embodiments, thediamond particles may include a portion exhibiting a relatively largersize (e.g., 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10μm, 8 μm) and another portion exhibiting at least one relatively smallersize (e.g., 15 μm, 12 μm, 10 μm, 8 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In anembodiment, the diamond particles may include a portion exhibiting arelatively larger size between about 10 μm and about 40 μm and anotherportion exhibiting a relatively smaller size between about 1 μm and 4μm. In another embodiment, the diamond particles may include a portionexhibiting the relatively larger size between about 15 μm and about 50μm and another portion exhibiting the relatively smaller size betweenabout 5 μm and about 15 μm. In another embodiment, the relatively largersize diamond particles may have a ratio to the relatively smaller sizediamond particles of at least 1.5. In some embodiments, the diamondparticles may comprise three or more different sizes (e.g., onerelatively larger size and two or more relatively smaller sizes),without limitation. The resulting polycrystalline diamond formed fromHPHT sintering the aforementioned diamond particles may also exhibit thesame or similar diamond grain size distributions and/or sizes as theaforementioned diamond particle distributions and particle sizes.Additionally, in any of the embodiments disclosed herein, the superhardbearing elements may be free-standing (e.g., substrateless) andoptionally may be at least partially or fully leached to remove ametal-solvent catalyst initially used to sinter the polycrystallinediamond body.

In some instances, high thermal load on one or more of the superhardbearing elements 120 a may produce temperatures that may degrade and/ordeteriorate associated one or more superhard tables 150 a. For example,at temperatures of above around 700° C., the polycrystalline diamond maydegrade under certain operating conditions, which may lead to thefailure of the superhard bearing elements 120 a and, thus, of thethrust-bearing assembly support ring structure 110 a. Therefore,maintaining the operating temperature of the superhard bearing elements120 a below detrimental temperature, such as by providing increasedsurface area of the superhard table 150 a that may be exposed to thecooling medium may increase useful life of the thrust-bearing assemblysupport ring structure 110 a.

For instance, the superhard table 150 a may have a maximum thickness(i.e., a height of the superhard table 150 a protruding above thesubstrate 160 a) of between about 0.100″ and about 0.140″; between about0.120″ and about 0.187″; between about 0.120″ and about 0.312″; betweenabout 0.156″ and about 0.250″; or between about 0.250″ and about 0.312″.In additional or alternative embodiments, the superhard table 150 a mayhave a maximum thickness that is greater than about 0.312″ or less. Insome embodiments, the superhard table 150 a may have a maximum thicknessthat is greater than about 0.1″, greater than about 0.2″, greater thanabout 0.3″, greater than about 0.4″, greater than about 0.5″, about0.50″ to about 0.75″, or greater than about 0.75″. In other words, theheight of one or more of the superhard bearing elements 120 a may becomprised entirely of the superhard table 150 a (i.e., the superhardbearing elements 120 a may have no substrate 160 a). On the one hand,increasing the thickness superhard table 150 a may increase theefficiency of transferring heat from the superhard bearing elements 120a, which may lead to an increased load-bearing capacity of thethrust-bearing assembly 100 a. On the other hand, increasing thethickness of superhard table 150 a may be costly and/or may increasemoment and/or shear forces experienced by the superhard bearing elements120 a (e.g., by the superhard table 150 a relative to the substrate 160a). Accordingly, a maximum thickness of the superhard table 150 a mayvary from one embodiment to the next. More specifically, among otherthings, a maximum thickness of the superhard table 150 a may depend onthe overall size of the thrust-bearing assembly 100 a and/or of thesuperhard bearing elements 120 a, particle size and/or density of thepolycrystalline diamond, load requirements, and the like.

In one or more embodiments, the superhard table 150 a may have themaximum thickness at and/or near a peripheral surface 121 a of thesuperhard bearing elements 120 a. For example, the superhard table 150 amay form or define a portion of the peripheral surface 121 a of thesuperhard bearing elements 120 a at the location of the maximumthickness of the superhard table 150 a. Accordingly, increasing themaximum thickness of the superhard table 150 a may increase the portionof the peripheral surface 121 a that is formed or defined by thesuperhard table 150 a, which may increase the overall exposure of thesuperhard table 150 a to the cooling medium.

More specifically, cooling medium may at least partially surround theportion of the superhard bearing elements 120 a that protrudes above thesupport ring structure 110 a, thereby cooling the superhard bearingelements 120 a. In one or more embodiments, the superhard table 150 amay have a relative high thermal conductivity (e.g., the superhard table150 a may include polycrystalline diamond that may have thermalconductivity of about 500 W/m·K or more). Accordingly, it is believedthat the heat generated at the bearing surface 122 a of the superhardbearing elements 120 a may be transferred to the peripheral surface 121a and may be further transferred to the cooling medium. Particularly,the portion of the peripheral surface 121 a that may be formed by thesuperhard table 150 a may provide efficient convective heat transferfrom the superhard bearing elements 120 a to the cooling medium.

In addition, the superhard bearing elements 120 a may protrude from thesupport ring structure 110 a in a manner that increases exposure of theperipheral surface 121 a and/or of the portion of the peripheral surface121 a formed by the superhard table 150 a. In other words, the superhardbearing elements 120 a may have an exposed protruding portion thatextends above a top surface of the support ring structure 110 a adistance 123 a (measured from top surface of the bearing element 120 ato the top surface of the support ring 140 a), which is equal to orgreater than the portion of the peripheral surface 121 a that is formedby the superhard table 150 a. Hence, in some embodiments, the superhardbearing elements 120 a may protrude above the support ring structure 110a to the distance 123 a that may be between about 0.090″ and about0.200″; between about 0.180″ and about 0.300″; between about 0.250″ andabout 0.400″; between about 0.300″ and about 0.500.″ In otherembodiments, the superhard bearing elements 120 a may protrude above thesupport ring structure 110 a to a height of about 0.90 (or more)multiplied by the thickness of the superhard table 150 a (e.g., a 0.100″thick polycrystalline diamond table multiplied by 0.90 equals 0.090″).In additional or alternative embodiments, the superhard bearing elements120 a may protrude above the support ring structure 110 a to a heightthat is greater than 0.500″. In other embodiments, the superhard bearingelements 120 a may protrude above the support ring structure 110 a to aheight that is greater than 0.090″.

As mentioned above, the superhard bearing elements 120 a may have anynumber of suitable peripheral surfaces. For instance, such peripheralsurfaces may maximize the ratio of the surface area of the peripheralsurface to the volume of the superhard table. In the embodimentillustrated in FIG. 1B, a thrust-bearing assembly 100 b may incorporatesuperhard bearing elements 120 b that may have polygonal bearingsurfaces 122 b and corresponding peripheral surfaces 121 b,circumscribing the polygonal bearing surfaces 122 b. Except as otherwisedescribed herein, the thrust-bearing assembly 100 b and its materials,components, or elements (e.g., superhard tables) may be similar to orthe same as the thrust-bearing assembly 100 a (FIG. 1A). For example,the thrust-bearing assembly 100 b may include a support ring structure110 b that may secure the superhard bearing elements 120 b.

The peripheral surface 121 b of the superhard bearing elements 120 b mayprovide increased surface area to volume ratio as compared with anapproximately cylindrical superhard bearing element. The peripheralsurface 121 b also may include a superhard table 150 b bonded or securedto a substrate 160 b. Furthermore, as described above, a portion of theperipheral surface 121 b may be formed or defined by the superhard table150 b. Accordingly, increasing the surface area to volume ratio of thesuperhard bearing elements 120 b also may decrease the volume of thesuperhard table 150 b per unit area of the peripheral surface 121 b thatmay be formed by the superhard table 150 b. In other words, cubicsuperhard bearing elements 120 b may use less polycrystalline diamondcompact in the superhard table 150 b to form the same surface area onthe peripheral surface 121 b as compared with a cylindrical superhardbearing elements (e.g., superhard bearing elements 120 a (FIG. 1A)).

In one or more embodiments, at least a portion of the peripheral surface121 b may have rounded or filleted corners, such as to facilitatemanufacturing of the thrust-bearing assembly 100 b (e.g., roundedcorners may allow recesses that may secure the superhard bearingelements 120 b to be conventionally machined). In addition, roundedcorners on the superhard bearing elements 120 b may reduce chipping,cracking, or otherwise breaking of the superhard table 150 b, which mayresult at or near substantially sharp corners. Likewise, providingrounded corners in the recesses that may secure the superhard bearingelements 120 b may reduce or eliminate strain- or stress-induced cracksthat may occur at sharp corners. However, an embodiment may include thesuperhard bearing elements 120 b that have a square or rectangularcross-section with substantially sharp corners, without limitation. Insuch embodiment, the recesses in the support ring structure also mayhave sharp corner (such recesses may be manufactured usingelectro-discharge machining (“EDM”), wire EDM, water jet cutting, etc.).

In some embodiments, the substrate 160 b and the superhard table 150 bmay have substantially the same cross-sectional size and shape. In otherembodiments, the substrate 160 b and the superhard table 150 b may havedifferent sizes and/or shapes from each other. For instance, thesubstrate 160 b may have a circular cross-sectional shape, while thesuperhard table 150 b may have a square or rectangular cross-sectionalshape. In an embodiment, a bottom of the superhard table 150 b may belocated above the support ring structure 110 b. Hence, for instance, acylindrical substrate may be located inside a cylindrical recess, and acubic superhard table 150 b may be bonded to the cylindrical substrateand may protrude above the support ring structure 110 b.

It should be appreciated that the superhard bearing elements also mayhave other shapes of the peripheral surfaces some of which may maximizethe ratio of volume of superhard table to surface area of the peripheralsurface. For instance, the peripheral surface of the superhard bearingelements 120 b may have a cuboid or a rectangular cross-section.Additionally or alternatively, the superhard bearing elements 120 b mayhave a triangular cross-section, which may further increase the surfacearea to volume ratio of the peripheral surface (as compared with asquare or rectangular cross-sectional shape).

In an embodiment, all or substantially all of the superhard bearingelements may be the same or similar to each other (e.g., all of thesuperhard bearing elements may include a superhard table). In anotherembodiment, a thrust-bearing assembly may include superhard bearingelements that have superhard tables exhibiting selected thicknesses,respectively, as well as superhard bearing elements that haveconventional or standard superhard tables. For example, FIG. 1Cillustrates a thrust-bearing assembly 100 c that incorporates superhardbearing elements 120 c, such as superhard bearing elements 120 c′ andsuperhard bearing elements 120 c″, which may include superhard tables ofdifferent thicknesses and/or configuration. Except as otherwisedescribed herein, the thrust-bearing assembly 100 c and its materials,components, or elements (e.g., bearing elements) may be similar to orthe same as any of the thrust-bearing assemblies 100 a, 100 b (FIGS. 1Aand 1B).

In one or more embodiments, the superhard bearing elements 120 c′ mayinclude a superhard table 150 c′, while the superhard bearing elements120 c″ may include a superhard table 150 c″. For example, superhardtable 150 c′ may have a thickness of between about 0.100″ and about0.140″; between about 0.120″ and about 0.187″; between about 0.156″ andabout 0.250″; or between about 0.250″ and about 0.312″. Embodiments mayinclude the superhard table 150 c″ having a thickness of less than0.120″, between about 0.020″ and about 0.040″; between about 0.030″ andabout 0.060″; between about 0.050″ and about 0.080″; or between about0.070″ and about 0.100″. For instance, under some operating conditions,one or more of the superhard bearing elements 120 c may experiencehigher forces and/or friction than other superhard bearing elements 120c. Particularly, the superhard bearing elements 120 c′ may be positionedin a manner that the superhard bearing elements 120 c′ experience higherforces and/or friction than the superhard bearing elements 120 c″. In anembodiment, the thrust-bearing assembly 100 c may include a single ormultiple superhard bearing elements 120 c′ located near or at one ormore location that may experience the greatest amount of force and/orshear, as compared with the superhard bearing elements 120 c″.

Conversely, the superhard bearing elements 120 c″ may experience lessforce and/or shear than the superhard bearing elements 120 c′. As such,thinner superhard tables 150 c″ of the superhard bearing elements 120 c″may provide sufficient heat dissipation for the superhard bearingelements 120 c″. It is believed that reduced force and/or frictionexperienced by the superhard bearing elements 120 c″ may produce orgenerate less heat, which may need to be dissipated, to avoid heatingthe superhard table 150 c″ to or above detrimental temperatures.Accordingly, because the superhard bearing elements 120 c″ and/or thesuperhard tables 150 c″ may require lower heat dissipation, thesuperhard table 150″ may be thinner than the superhard table 150 c′ ofthe superhard bearing elements 120 c′.

The superhard bearing elements 120 c″ may include the superhard table150 c″ that may have any number of suitable thicknesses, which may varyfrom one embodiment to another. For example, the thickness of thesuperhard table 150 c″ may depend on the material used therein, loadscarried by the superhard bearing elements 120 c″, amount of coolingprovided by the cooling medium, and the like. In one or moreembodiments, the thickness of the superhard table 150 c″ may be lessthan 0.100″. Specifically, the thickness of the superhard table 150 c″may be between about 0.040″ and about 0.060″; between about 0.050″ andabout 0.080″; or between about 0.070″ and thrust-bearing assembly 100″.It should be appreciated that, in some instances, the thickness of thesuperhard table 150 c″ may be less than 0.040″. It should be appreciatedthat, in an embodiment, the superhard bearing elements 120 c′ and thesuperhard bearing elements 120 c″ may include bearing surfaces 122 cthat are substantially coplanar with each other.

In an embodiment, the thrust-bearing assembly also may provide increasedexposure to cooling fluid on one or more sides of the bearing elements.FIG. 1D illustrates an embodiment of a thrust-bearing assembly 100 a′that has more exposure of superhard bearing elements 120 d on an outerside of a support ring structure 110 d than on an inner side thereof.Except as otherwise described herein, the thrust-bearing assembly 100 dand its materials, components, or elements (e.g., bearing elements) maybe similar to or the same as any of the thrust-bearing assemblies 100 a,100 b, 100 c (FIGS. 1A, 1B, and 1C). For instance, the superhard bearingelements 120 d of the thrust-bearing assembly 100 d may be the same asany of the superhard bearing elements 120 a, 120 b, 120 c′, 120 c″(FIGS. 1A, 1B, and 1C).

In one embodiment, the support ring structure 110 a′ of thethrust-bearing assembly 100 a′ includes an outer side 111 a′ and aninner side 112 a′. Particularly, the outer side 111 a′ may define anoutside diameter of the support ring structure 110 a′. Similarly, theinner side 112 a′ may define the inside diameter of the support ringstructure 110 a′. Furthermore, as mentioned above, the outer side 111 a′may have a first height that is smaller than a second height of theinner side 112 a′. As such, the superhard bearing elements 120 a′ mayhave more exposure to fluid on the outer side 111 a′ than on the innerside 112 a′ (i.e., the superhard bearing elements 120 a′ may have afirst distance 123 a′ from the top of the support ring structure 110 a′on the outer side 111 a′ to the bearing surface 122 and a seconddistance 124 a′ from the top of the support ring structure 110 a′ on theinner side 112 a′ to the bearing surface 122). Also, increased height ofthe inner side 112 a′ of the support ring structure 110 a′ (relative tothe height of the outer side 111 a′) may provide increased support tothe superhard bearing elements 120 a′, which may allow thethrust-bearing assembly 100 a′ to carry a greater load, as compared witha thrust-bearing assembly with equal inner and outer heights.

In addition to various shapes and configurations of the peripheralsurface, the superhard bearing elements also may include variousconfigurations of the superhard table, which may vary from oneembodiment to the next. FIGS. 2A-2F illustrate embodiments of thesuperhard bearing elements that include various superhard tables.Generally, except otherwise described herein, any of the superhardbearing elements illustrated in FIGS. 2B-2F may have a peripheralsurface that has the same or similar shape and/or size as a peripheralsurface 121 of the superhard bearing element 120, illustrated in FIG.2A. Moreover, any of the thrust-bearing assemblies 100 a, 100 b, 100 c(FIGS. 1A-1C) may include any of the superhard bearing elementsillustrated in FIGS. 2A-2F as well as combinations thereof.

In some embodiments, the superhard bearing element 120 may include asuperhard table 150 bonded to a substrate 160. The superhard table 150may include the bearing surface 122 of the superhard bearing element120. Together, the superhard table 150 and the substrate 160 may form ordefine the peripheral surface 121.

More specifically, in one embodiment, the peripheral surface 121 maycomprise a superhard portion 123 that may be formed by the superhardtable 150 and a substrate portion 124, which may be formed by thesubstrate 160. As noted above, an embodiment includes the superhard andsubstrate portions 123, 124 of the peripheral surface 121 that havesimilar or the same outer sizes and shapes. In other words, theperipheral surface 121 may have no gaps, breaks, or significantimperfections between the superhard and substrate portions 123, 124thereof. In alternative or additional embodiments, the superhard andsubstrate portions 123, 124 may have different sizes and/or shapes. Forinstance, the superhard portion 123 may have a cubic prismoid or cuboidshape, while the substrate portion 124 may have a cylindrical shape.

Also, the surface area of the bearing surface 122 may have apredetermined ratio to the surface area of the superhard portion 123 ofthe peripheral surface 121. In an embodiment, the superhard portion 123may have an approximately cylindrical shape, which may define anapproximately circular perimeter of the bearing surface 122. Hence, inan embodiment, the ratio of the bearing surface 122 to the superhardportion 123 of the peripheral surface 121 may be approximately 4:1 ormore. In another embodiment, the ratio of the bearing surface 122 to thesuperhard portion 123 may be approximately 2:1 or more. It should beappreciated that the ratio of the bearing surface 122 to the superhardportion 123 may be greater than 4:1 or less than 2:1.

In some embodiments, the bearing surface 122 may be substantially planaror flat, which may facilitate use of the superhard bearing elements 120in a thrust-bearing assembly and apparatus. In additional or alternativeembodiments, the superhard bearing elements 120 may have a curvedbearing surface 122. For instance, in an embodiment, the bearing surface122 may have a convex curvature. Similarly, in another embodiment, thebearing surface 122 may have a concave curvature. As described below infurther detail, the superhard bearing elements 120 having convexlyand/or concavely curved bearing surface 122 may be included inradial-bearing assemblies and apparatuses.

As illustrated in FIG. 2B, in some embodiments, a superhard bearingelements 120 c may have a substantially flat interface 125 c between asuperhard table 150 c and a substrate 160 c. In other words, thesuperhard table 150 c may have a substantially uniform profile that mayhave approximately the same thickness throughout (e.g., the thickness ofthe superhard table 150 c may vary across the substrate 160 c aftergrinding and/or lapping of the bearing surface of the superhard bearingelements 120 c). As noted above, the superhard bearing elements 120 cmay include a peripheral surface 121 c that has a superhard portion 123c defined or formed by the superhard table 150 c and a substrate portion124 c, which may be defined or formed by the substrate 160 c. In anembodiment, the thickness of the superhard table 150 c may beapproximately the same as the height of the superhard portion 123 c ofthe peripheral surface 121 c.

As illustrated in FIG. 2C, an embodiment also may include a superhardbearing element 120 d that may have a curved interface 125 d between ansuperhard table 150 d and a substrate 160 d. Particularly, the curvedinterface 125 d may have a curvilinear surface, which may vary along twoor three dimensions. For example, the curved interface 125 d mayapproximate a convex hemispherical or a partially convex sphericalsurface, such that the distance from a bearing surface 122 d to thecurved interface 125 d increases with the distance from a center of thesuperhard bearing element 120 d to a peripheral surface 121 d thereof.

Alternatively, the curved interface 125 d may have an approximatelypartially concave cylindrical surface, such that the distance from acenter of the superhard bearing element 120 d to the peripheral surface121 d decreases along a first dimension, while remaining approximatelyconstant along a second dimension. It should be appreciated, however,that the curved interface 125 d may have any number of shapes,configurations, orientations, and the like. Hence, embodiments mayinclude curved interface 125 d that may have other curvilinear shapesand/or sizes (e.g., elliptical surface, irregular curved surfaces,etc.).

In an embodiment, the peripheral surface 121 d may include a superhardportion 123 d defined or formed by the superhard table 150 d and asubstrate portion 124 d, which is defined or formed by the substrate 160d. In an embodiment, the superhard portion 123 d of the peripheralsurface 121 d may have a height that is greater than the averagethickness of the superhard table 150 d. As such, the superhard bearingelement 120 d may have an increased ratio of surface area of thesuperhard portion 123 d of the peripheral surface 121 d to the volume ofthe superhard table 150 d, as compared with the superhard bearingelement 120 c that has the flat interface 125 c (FIG. 2B). Thus, thesuperhard bearing element 120 d (e.g., as compared with superhardbearing element 120 c) may be more cost effective to manufacture and mayexhibit the same or similar efficiency in dissipating heat from thesuperhard table 150 d and/or superhard bearing element 120 d as thesuperhard bearing element 120 c (FIG. 2B).

In an alternative embodiment, as illustrated in FIG. 2D, a superhardbearing element 120 e may include a substantially conical interface 125e between the superhard table 150 e and substrate 160 e. In anembodiment, the conical interface 125 e may form a peak at an uppermostpoint thereof. Specifically, the peak of the conical interface 125 e maybe the closest portion thereof to a bearing surface 122 e of thesuperhard bearing element 120 e. In some instances, the peak may beapproximately aligned with a central axis of the superhard bearingelement 120 e. In other embodiments, the peak may be located off centerfrom the central axis. Moreover, in at least one embodiment, the peakmay include a radius or a chamfer (or a flat area) that may reducestress, which may otherwise occur at a substantially sharp point of thepeak.

Further embodiments may include superhard bearing elements that have anyother selected interface between the superhard table and the substrate.For instance, FIG. 2E illustrates a superhard bearing element 120 f thatmay include a stepped interface 125 f between a superhard table 150 fand a substrate 160 f. As mentioned above, the superhard bearing element120 f may be substantially cylindrical. In an embodiment, one or moreplanes of the stepped interface 125 f may be approximately circular. Forexample, the stepped interface 125 f may include a first surface 126 fand a second surface 127 f each of which has a substantiallycircular-shaped outer perimeter. Furthermore, the first and secondsurfaces 126 f, 127 f may be located at different heights relative to abearing surface 122 f of the superhard bearing element 120 f. In otherwords, the superhard table 150 f may have a different thickness alongthe first surface 126 f than along the second surface 127 f. In anembodiment, the superhard table 150 f may be thicker along the secondsurface 127 f than along the first surface 126 f. Optionally, first andsecond surfaces 126 f and/or 127 f may be textured, grooved, dimpled,combinations thereof, or otherwise non-planar.

As described above, the superhard bearing element 120 f may have aperipheral surface 121 f that may include a superhard portion 123 f(e.g., an annular portion) formed or defined by the superhard table 150f and a substrate portion 124 f, which may be formed or defined by thesubstrate 160 f. In some embodiments, the superhard portion 123 f mayhave a height (i.e., a distance from the substrate portion 124 f to abearing surface 122 f of the superhard bearing element 120 f) that isgreater than the average thickness of the superhard table 150 f. Forinstance, the thickness of the superhard table 150 f along the firstsurface 126 f may be less than the thickness of superhard table 150 falong the second surface 127 f, which may form or define the superhardportion 123 f of the peripheral surface 121 f.

Embodiments also may include superhard bearing elements that include astepped interface that has one or more transition regions between themajor surfaces thereof. FIG. 2F illustrates a superhard bearing element120 g that has a stepped interface 125 g between an superhard table 150g and a substrate 160 g. Specifically, the stepped interface 125 g ofthe superhard bearing element 120 g may include a first surface 126 g, asecond surface 127 g, and a transition region 128 g that may extendbetween the first and second surfaces 126 g, 127 g. The first and/orsecond surfaces 126 g, 127 g may be substantially the same as the firstand/or second surfaces 126 f, 127 f (FIG. 2E). In some instances, thesurface of the transition region 128 g may have a non-orthogonalorientation relative to the first and/or second surfaces 126 g, 127 g.As such, in addition to the first and second surfaces 126 g, 127 g, thetransition region 128 g may carry at least a portion of the loadsupported by the superhard bearing element 120 g.

Furthermore, the thickness of the superhard table 150 g, as measuredfrom the first surface 126 g, may be substantially less than thethickness of the superhard table 150 g on the second surface 127 g. Inother words, the superhard table 150 g may have a first distance fromthe first surface 126 g to a bearing surface 122 g and a second distancefrom the second surface 127 g to the bearing surface 122 g, where thefirst distance is substantially smaller than the second distance. Forexample, the first distance may be between about 0.040″ to about 0.080″;between about 0.060″ to about 0.120″; or between about 0.100″ to about0.150″. The second distance may be between about 0.120″ to about 0.180″;between about 0.150″ to about 0.250″; between about 0.200″ to about0.300″, and, in some instances, may be greater than 0.003″, greater than0.400″, or greater than 0.500″, such as between about 0.300″ to about0.400,″ between about 0.400″ to about 0.500,″ or between about 0.500″ toabout 0.600″. It should be appreciated that in some embodiments, thefirst distance may be less than 0.040″ or greater than 0.150″. Likewise,the second distance may be less than about 0.040″ and greater than0.600″.

As described above, the superhard bearing element 120 g may have aperipheral surface 121 g that may include a superhard portion 123 gformed or defined by the superhard table 150 g and a second portion,which may be formed or defined by the substrate 160 g. Including thestepped interface 125 g between the superhard table 150 g and thesubstrate 160 g may provide a higher ratio of the height of thesuperhard table 150 g that may be exposed to the cooling medium (i.e.,the height of the superhard portion 123 g of the peripheral surface 121g) to the average thickness of the superhard table 150 g. In any event,the superhard portion 123 g of the peripheral surface 121 may facilitatesufficient convective heat transfer from the superhard bearing element120 g to the cooling medium.

As noted above, any of the superhard bearing elements described hereinmay be included in any thrust-bearing assembly. Furthermore, any of thethrust-bearing assemblies described herein may be incorporated in athrust-bearing apparatus. FIG. 3 illustrates an embodiment of athrust-bearing apparatus 200, which may incorporate any of thethrust-bearing assemblies 100 a, 100 b, 100 c (FIGS. 1A-1C) as a statorand/or a rotor. Specifically, the thrust-bearing apparatus 200 mayinclude first and second thrust-bearing assemblies thrust-bearingassemblies 100 h′, 100 h″. The first thrust-bearing assembly 100 h′ maybe the stator that remains stationary, while the second thrust-bearingassembly 100 h″ may be the rotor that may rotate relative to the stator,or vice versa.

Each of the first thrust-bearing assembly 100 h′ and the secondthrust-bearing assembly 100 h″ may include multiple generally opposingsuperhard bearing elements 120 h (e.g., superhard bearing elements 120h′, 120 h″) that face and engage one another, which may be mounted in oron support ring structures 110 h (i.e., respective support ringstructures 110 h′, 110 h″). Additionally, the superhard bearing elements120 h′, 120 h″ may have bearing surfaces 122 h, such as bearing surfaces122 h′, 122 h″, respectively. In particular, the bearing surfaces 122 h′may generally oppose and engage the bearing surfaces 122 h″. As such,the superhard bearing elements 120 h may prevent relative axial movementof the first thrust-bearing assembly 100 h′ and the secondthrust-bearing assembly 100 h′″ (along the thrust axis 10 a), whileallowing the second thrust-bearing assembly 100 h″ to rotate relative tothe first thrust-bearing assembly 100 h′ about the thrust axis 10 a.

Moreover, the first thrust-bearing assembly 100 h′ and/or the secondthrust-bearing assembly 100 h″ may include openings 130 h. A shaft, suchas an output shaft of the subterranean drilling system, may fit throughand/or may be secured within one of the openings 130 h. For example, theshaft may fit through the opening 130 h of the first thrust-bearingassembly 100 h′ in a manner that the shaft may freely rotate within theopening 130 h of the first thrust-bearing assembly 100 h′ and may besecured to the second thrust-bearing assembly 100 h″.

Although the thrust-bearing apparatus 200 described above mayincorporate multiple superhard bearing elements 120 h that havecorresponding bearing surfaces 122 h, it should be appreciated that thisis one of many embodiments. For example, one of the first thrust-bearingassembly 100 h′ or the second thrust-bearing assembly 100 h″ may includea single superhard bearing element that spans substantially an entirecircumference thereof. In other words, the superhard bearing element mayform a single or substantially uninterrupted bearing surface that mayspan the entire circumference of the first and/or second thrust-bearingassemblies 100 h′, 100 h″. Furthermore, the first thrust-bearingassembly 100 h′ and/or the second thrust-bearing assembly 100 h″ mayhave any number of the superhard bearing elements 120 h that may bespaced apart from each other in any desired configuration, which mayvary from one embodiment to another. For instance, in some embodiments,the superhard bearing elements 120 h may overlap about or be spacedclosely together, thereby forming a substantially continuous bearingsurface 122 h.

In additional or alternative embodiments, the thrust-bearing apparatusmay include only a single thrust-bearing bearing assembly (e.g., thefirst or second thrust-bearing assembly 100 h′, 100 h″). For example,the bearing surfaces 122 h of the first thrust-bearing assembly 100 h′may engage a component or element of a machine, which may be stationaryor may be moveable relative to the first thrust-bearing assembly 100 h′.In an embodiment, the bearing surfaces 122 h′ of the firstthrust-bearing assembly 100 h′ may engage a substantially flat platethat may be secured to a rotating element or component of a machine ormechanism that incorporates the first thrust-bearing assembly 100 h′.

In one or more embodiments, the thrust-bearing apparatus 200 may includea space between the support ring structures 110 h′, support ringstructure 110 h″ (e.g., the space formed by the protruding superhardbearing elements 120 h). Such space may accommodate entry and/orpass-through of the cooling medium (e.g., drilling mud), which maytransfer or remove heat from the thrust-bearing apparatus 200 as well ascomponents or elements thereof (e.g., from the support ring structure110 h and from the superhard bearing elements 120 h). Increasing thespace between the support ring structures 110 h′, 110 h″ may increaseand/or may allow an increased flow or pass-through of the cooling mediumthrough the thrust-bearing apparatus 200. As noted above, the firstand/or second thrust-bearing assemblies 100 h′, 100 h″ may includesuperhard bearing elements 120 h that may protrude to a greater degree,as compared with standard bearing elements. Consequently, such superhardbearing elements 120 h, as provided by this disclosure, may create aselected gap 123 h between the support ring structures 110 h′, 110 h″and may increase the flow of cooling medium through the thrust-bearingapparatus 200. Increased flow of the cooling medium, in turn, may leadto increased heat transfer from the thrust-bearing apparatus 200 (ascompared with a thrust-bearing apparatus having a conventional gapbetween the support ring structures).

Particular size or dimension of the gap 123 h between the support ringstructures 110 h′, 110 h″ may vary from one embodiment to the next.Among other things, the dimension of the gap 123 h may depend on theforces and/or friction experienced by the superhard bearing elements 120h, type of the cooling medium that circulates through the thrust-bearingapparatus 200, etc. Furthermore, the gap 123 h may not be uniformthroughout the thrust-bearing apparatus 200. In other words, at somelocations, dimension of height of the gap 123 h may be greater than thedimension at other locations thereof. In any event, in some embodiments,the gap 123 h may include at least one dimension that is in one or moreof the following ranges: between about 0.200″ and about 0.400″; betweenabout 0.300″ and about 0.600″; between about 0.200″ and about 1.00″, orbetween about 0.500″ and 1.00″. It should be appreciated, however, thatthe gap 123 h also may have at least one dimension (e.g., a height) thatis greater than 1.00″.

Tests were performed with various thrust-bearing apparatuses to quantifythe advantages provided by the thrust-bearing apparatus 200 and variantsthereof. Specifically, tested thrust-bearing apparatuses were subjectedto a constant speed (i.e., the rotor was rotated at a constant speed,while the stator was held stationary) and to an increasing load, whichwas increased at a target rate of 3 lbf/sec until failure of the testedthrust-bearing apparatus. To identify failure of the testedthrust-bearing apparatus, torque was monitored: prior to failure, thetorque increased generally linearly with corresponding increase of theload; after the failure, torque exhibited nonlinear increase withincreased load. After the failure was detected, experiment was stoppedand applied force was recorded. In addition, failure of the testedthrust-bearing apparatuses and/or superhard bearing elements wasconfirmed visually, by inspecting the failed thrust-bearing apparatuses.

Furthermore, the tested thrust-bearing apparatuses included 17-4stainless steel support rings to which the superhard bearing elementswere mounted, which were approximately 0.640″ in diameter. In oneexperiment, a first configuration of a thrust-bearing apparatus includedthe superhard bearing elements that protruded about 0.065″ above thesupport ring and included superhard bearing table having about 0.050″thickness, which included a standard polycrystalline diamond (i.e., astandard polycrystalline diamond compact including a polycrystallinediamond table formed from about 40 μm diamond particle size feedstockbonded to a cobalt-cemented tungsten carbide substrate). Thepolycrystalline diamond compacts were HPHT processed at a cell pressureof about 5 GPa to sinter the diamond particle feedstock to form thepolycrystalline diamond table. The thrust-bearing apparatuses having thefirst configuration were tested twice: (i) during the first test, thefirst configuration of the thrust-bearing apparatus exhibited failure atabout 15,500 lbf; (ii) during the second test, the first configurationof the thrust-bearing apparatus exhibited failure at about 19,000 lbf.

A second configuration of the thrust-bearing apparatus included thesuperhard bearing elements that had superhard bearing table having0.065″ thickness, which included a polycrystalline diamond (i.e.,polycrystalline diamond compact including a polycrystalline diamondtable formed from about 19 μm diamond particle size feedstock bonded toa cobalt-cemented tungsten carbide substrate). The polycrystallinediamond compacts were HPHT processed at a relatively more extreme cellpressure to sinter the diamond particle feedstock to form thepolycrystalline diamond table compared to the superhard bearing elementsof the first configuration. The thrust-bearing apparatuses having thesecond configuration were tested twice: (i) during the first test, thesecond configuration of the thrust-bearing apparatus exhibited failureat about 19,000 lbf; (ii) during the second test, the secondconfiguration of the thrust-bearing apparatus exhibited failure at about19,500 lbf.

In addition, one embodiment of the thrust-bearing apparatus 200 (FIG. 3)was tested. More specifically, the thrust-bearing apparatus 200 includedsuperhard bearing elements 120 h that had superhard table having 0.100″thickness, which was formed of polycrystalline diamond bonded to acobalt-cemented tungsten carbide substrate. In an embodiment, thesuperhard bearing elements 120 h may protrude about 0.120″ above thesupport ring. Additionally, the thrust-bearing apparatuses 200 withsuperhard bearing elements were subjected to substantially the same testas the thrust-bearing apparatuses of the first and secondconfigurations, described above. The thrust-bearing apparatuses 200 alsowere tested twice: (i) during the first test, the thrust-bearingapparatus 200 exhibited failure at about 33,000 lbf; (ii) during thesecond test, the thrust-bearing apparatus 200 exhibited failure at about34,000 lbf.

As clearly apparent, the thrust-bearing apparatuses 200 provided asuperior load-carrying capability as compared with the otherthrust-bearing apparatuses. It is believed that superior heat transfercapability of the superhard bearing elements 120 h of the thrust-bearingapparatus 200 facilitates sufficient heat transfer from the superhardbearing elements 120 h to prevent the temperature of the superhardtables thereof from reaching detrimental or damaging levels. In otherwords, the superhard bearing elements 120 h used in the experiments werebelieved to have maintained a temperature of the superhard tables belowabout 700° C., at least until the load was increased to about over33,000 lbf.

Although the above embodiments were described in connection with thethrust-bearing apparatuses and assemblies, it should be appreciated thatother embodiments are directed to radial-bearing apparatuses andassemblies. For instance, FIGS. 4A-4D illustrate embodiments ofradial-bearing assemblies that may comprise radial-bearing apparatuses.Except as described herein, the radial-bearing assemblies illustrated inFIGS. 4A-4D and described below, as well as their respective materials,elements, or components, may be similar to or the same as any ofthrust-bearing assemblies 100 a, 100 b, 100 c, 100 h (FIGS. 1A-3) andtheir respective materials, elements, or components (FIGS. 1A-3). Forexample, any of the bearing elements included in the radial-bearingassemblies of FIGS. 4A-4D may be similar to or the same as any of thesuperhard bearing elements 120-120 h (FIGS. 1A-3).

Specifically, FIG. 4A illustrates a first radial-bearing assembly 300 athat may include superhard bearing elements 120 k that may have ansuperhard table 150 k and a substrate 160 k. In particular, thesuperhard bearing elements 120 k may be secured to a support ringstructure 310 a. The superhard bearing elements 120 k also may bepositioned about a rotation axis 10 b. For example, the superhardbearing elements 120 k may be positioned circumferentially about therotation axis 10 b.

In an embodiment, the superhard bearing elements 120 k may define anopening 320 a, which may accommodate a second radial-bearing assemblythat may include bearing elements that may engage the superhard bearingelements 120 k. In particular, the bearing elements of the secondradial-bearing assembly may engage the superhard bearing elements 120 kin a manner that permits relative radial rotation of the firstradial-bearing assembly 300 a and the second radial bearing assembly butlimits relative lateral movement thereof, as described below.

Accordingly, at least one, some of, or each superhard bearing element330 a may include a superhard table (further described below) that has aconcave bearing surface 122 k (e.g., curved to form an interior surfaceof an imaginary tubular cylinder). Similarly, at least one, some of, oreach superhard bearing element of the second radial-bearing assembly(described below) may include a superhard table that has a convexbearing surface (e.g., curved to form at least a portion of an exteriorsurface of an imaginary cylinder or sphere). In any event, the concavebearing surface 122 k and the convex bearing surface may be shaped,sized, positioned, and oriented to generally correspond with and engageone another during operation of the radial-bearing apparatus.

Also, the support ring structure 310 a may define an outer perimeter(e.g., an outer diameter) of the first radial-bearing assembly 300 a.Furthermore, the support ring structure 310 a may include supportsurfaces or areas that may couple or may be secured to a stationaryportion of a device or mechanism. For instance, the support ringstructure 310 a of the first radial-bearing assembly 300 a may befixedly secured to a housing of the subterranean drilling system.Accordingly, as further described below, a radial-bearing apparatus thatincludes the first radial-bearing assembly 300 a may facilitate rotationof an output shaft relative to a housing about the rotation axis 10 b.

As described above, at least one, some of, or each superhard bearingelements 120 k may have superhard table 150 k of the same or similarsize (e.g., thickness and/or area of the superhard table 150 k) and/orconfiguration (e.g., interface between the superhard table 150 k and thesubstrate 160 k). Furthermore, the superhard bearing elements 120 k mayprotrude inward (i.e., toward the rotation axis 10 b) and away from thesupport ring structure 310 a to a distance 323 a, which may besufficient to expose the entire superhard table 150 k to cooling fluid.

Additionally or alternatively, at least one, some of, or each superhardbearing element 120 k may have differently sized superhard table. FIG.4B illustrates a first radial-bearing assembly 300 b that includessuperhard bearing elements 120 k that may have an superhard table 150 kas well as superhard bearing elements 120 k′ that may include standardsuperhard table 150 k′. Similar to the first radial-bearing assembly 300a (FIG. 4A), the superhard bearing elements 120 k, 120 k′ of the firstradial-bearing assembly 300 b may protrude toward the center of thesupport ring structure 310 a thereof to a distance of 323 b, which maybe sufficient to expose entire superhard tables 150 k, 150 k′ of some orall of the superhard bearing elements 120 k, 120 k′. In an embodiment,the superhard bearing elements 120 k may be located at or near a portionof the first radial-bearing assembly 300 b that may experience higherforces or friction than other portion(s) of the first radial-bearingassembly 300 b. In other words, the superhard bearing elements 120 k mayexperience and/or carry higher forces than the superhard bearingelements 120 k′.

For example, the rotation axis 10 b may be oriented at a non-parallelangle relative to the vector of the gravitational pull of the Earth.Accordingly, weight of the machine elements or unbalanced weightdistribution of components coupled to or supported by the firstradial-bearing assembly 300 b and/or by the second radial-bearingassembly may apply uneven forces to superhard bearing elements 120 k ascompared with superhard bearing elements 120 k′. For instance, a shaftconnected to the second radial-bearing assembly and the housing securingthe first radial-bearing assembly 300 b may be oriented approximatelyhorizontally or perpendicularly to the direction of Earth'sgravitational pull. As such, the superhard bearing elements 120 k may bepositioned along a lower portion of the radial-bearing assembly 300 b(i.e., below a horizontal centerline of the radial-bearing assembly 300b) may experience higher forces and/or friction than the superhardbearing elements 120 k that may be positioned along an upper portion ofthe radial-bearing assembly 300 b.

Consequently, as mentioned above, one or more superhard bearing elements120 k also may experience higher thermal loads thereon than thesuperhard bearing elements 120 k′. Thus, in at least one embodiment, thesuperhard table 150 k with a selected thickness and/or exposure distancemay facilitate increased heat transfer from the superhard bearingelements 120 k to a cooling medium. For example, the superhard bearingelements 120 k may limit operational temperatures to limit or preventdamage or degradation of the superhard bearing elements 120 k and/orsuperhard table 150 k.

In additional or alternative embodiments, as illustrated in FIG. 4C, aradial-bearing assembly 300 c may include superhard bearing elements 120m, which may have an superhard table 150 m bonded to or mounted on asubstrate 160 m. Particularly, the superhard bearing elements 120 m maybe located at or near the portion of the first radial-bearing assembly300 c that may experience or may be predicted to experience higherforces. In an embodiment, the first radial-bearing assembly also mayinclude superhard bearing elements 120 k′. For instance, the superhardbearing elements 120 m may include a bearing surface 122 m that may besubstantially larger (i.e., in surface area) than a bearing surface 122k′ of the superhard bearing elements 120 k′ (e.g., the bearing surface122 m may have a surface area ratio of 2:1, 3:1, etc. to the bearingsurface 122 k′). In some embodiments, the bearing surface 122 m may beformed from multiple superhard bearing elements 120 m positioned near orin contact with each other. Alternatively, the bearing surface 122 m maybe on a single superhard bearing element 120 m. In any event, thesuperhard bearing element(s) 120 m may have a substantially largerbearing surface as compared with the superhard bearing elements 120 k′.

As noted above, the radial-bearing apparatus may include a secondradial-bearing assembly that may be located inside the firstradial-bearing assembly. FIG. 4D illustrates one embodiment of a secondradial-bearing assembly 350 that may include superhard bearing elements120 m secured to or within a support ring structure 360. Except asotherwise described herein, the second radial-bearing assembly 350 andits materials, elements, or components may be similar to or the same asany of the first radial-bearing assemblies 300 a, 300 b, 300 c (FIGS.4A-4C) and their respective material, elements, or components. In anembodiment, the superhard bearing elements 120 m may be positioned andoriented on the support ring structure 360 in a manner that thesuperhard bearing elements 120 m may engage corresponding bearingelements of any of the first radial-bearing assemblies 300 a, 300 b, 300c (FIGS. 4A-4C), as described above. In other words, the superhardbearing elements 120 m may include a superhard table 150 n having aselected thickness and a convex bearing surface 122 n, which maycorrespond to concave bearing surface(s) of the first radial-bearingassembly.

In an embodiment, all of the bearing elements of the secondradial-bearing assembly 350 may be superhard bearing elements 120 n,which may include a superhard table 150 n with a selected thicknessbonded to or mounted on a substrate 160 n. In additional or alternativeembodiments, similar to the first radial-bearing assemblies, the secondradial-bearing assembly 350 may include one or more bearing elementsthat may have a superhard table with a conventional thickness.Furthermore, in an embodiment, the second radial-bearing assembly 350may include superhard bearing elements 120 n that are positioned near orin contact with each other, and which may form a bearing surface that issubstantially larger than bearing surfaces of other bearing elements ofthe second radial-bearing assembly. Such configurations may accommodateloads that may be unevenly distributed about the second radial-bearingassembly 350.

Similar to the first radial-bearing assemblies, the secondradial-bearing assembly 350 may include superhard bearing elements 120 narranged in any number of suitable configurations, orientations, andpositions. For instance, the superhard bearing elements 120 n may bearranged in a single row, in two rows, three rows, four rows, or anyother number of rows. In any event, as mentioned above, the superhardbearing elements 120 n may be arranged in a manner that allows thesuperhard bearing elements 120 n to contact and/or slide against thebearing elements of the first radial-bearing assembly.

Accordingly, in an embodiment, the first and second radial-bearingassemblies may be engaged together to form a radial-bearing apparatus.FIG. 5 illustrates an embodiment of a radial-bearing apparatus 400. Theconcepts used in the thrust-bearing apparatuses described above also maybe employed in radial-bearing apparatuses. Furthermore, except asotherwise described herein, the radial-bearing apparatus 400 and itsmaterials, components, or elements may be similar to or the same as anyof the thrust-bearing assemblies or apparatus 100 a, 100 b, 100 c, 200(FIGS. 1-3) and their respective materials, components, or elements. Inaddition, the radial-bearing apparatus 400 may incorporate any of thefirst radial-bearing assemblies 300 a, 300 b, 300 c and the secondradial-bearing assembly 350 (FIGS. 4A-4D).

Particularly, in an embodiment, the radial-bearing apparatus 400 mayinclude first and second radial-bearing assemblies 300, 350, which mayinclude corresponding superhard bearing elements 120 p′, superhardbearing elements 120 p″, any of which may be similar to or the same asany of superhard bearing elements 120-120 n (FIGS. 1A-4D). Likewise, thesuperhard bearing elements 120 p′, superhard bearing elements 120 p″ mayhave corresponding bearing surfaces 122 p (i.e., bearing surfaces 122p′, bearing surface 122 p″) that may contact one another in a mannerthat allow the first and second radial-bearing assemblies 300, 350 torotate relative to each other, while limiting or preventing lateralmovement thereof. It should be appreciated that the first secondradial-bearing assembly 300 may be a stator, while the and secondradial-bearing assembly 350 may be a rotor or vice versa.

In an embodiment, a shaft (e.g., a drill shaft) or other machinecomponent or element may pass into or through an opening 370 of theradial-bearing apparatus 400 and may be secured to the secondradial-bearing assembly 350. Accordingly, the drill shaft may be rotatedtogether with the second radial-bearing assembly 350, while the firstradial-bearing assembly 300 remains stationary. For instance, the firstradial-bearing assembly 300 may be coupled to a housing and may remainstationary relative thereto as well as relative to the shaft.

As described above, selecting a protrusion distance for superhardbearing elements, such as the superhard bearing elements 120 p, mayprovide a selected gap 123 p between a support ring structure 310 of thefirst radial-bearing assembly 300 and a support ring structure 360 ofthe second radial-bearing assembly 350. As such, the selected gap 123 pmay allow an increased flow or amount of cooling medium to pass throughthe radial-bearing apparatus 400, as compared with a conventionalradial-bearing apparatus. Accordingly, as compared with a conventionalradial-bearing apparatus, in addition to or in lieu of increased heattransfer that may be provided by the superhard bearing elements 120 p(including by the relatively thick superhard tables thereof), theradial-bearing apparatus 400 may have increased heat transfer due to anincreased flow of cooling medium therethrough.

Any of the embodiments for thrust-bearing apparatuses and radial bearingapparatuses discussed above may be used in a subterranean drillingsystem. FIG. 6 is a schematic isometric cutaway view of a subterraneandrilling system 500 according to an embodiment. The subterraneandrilling system 500 may include a housing 560 enclosing a downholedrilling motor 562 (i.e., a motor, turbine, or any other device capableof rotating an output shaft) that may be operably connected to an outputshaft 556. A thrust-bearing apparatus 564 may be operably coupled to thedownhole drilling motor 562. The thrust-bearing apparatus 564 may beconfigured as any of the previously described thrust-bearing apparatusembodiments. A rotary drill bit 568 may be configured to engage asubterranean formation and drill a borehole and may be connected to theoutput shaft 556. The rotary drill bit 568 is a fixed-cutter drill bitand is shown comprising a bit body 590 having radially-extending andlongitudinally-extending blades 592 with a plurality of PDCs secured tothe blades 592. However, other embodiments may utilize different typesof rotary drill bits, such as core bits and/or roller-cone bits. As theborehole is drilled, pipe sections may be connected to the subterraneandrilling system 500 to form a drill string capable of progressivelydrilling the borehole to a greater size or depth within the earth.

The thrust-bearing apparatus 564 may include a stator 572 that does notrotate and a rotor 574 that may be attached to the output shaft 556 androtates with the output shaft 556. As discussed above, thethrust-bearing apparatus 564 may be configured as any of the embodimentsdisclosed herein. For example, the stator 572 may include a plurality ofcircumferentially-distributed superhard bearing elements 576 similar tothe superhard bearing elements 120 h shown and described in thethrust-bearing apparatus 200 of FIG. 3 as well as any of the superhardbearing elements 120-120 g (FIGS. 1A-2F) and combinations thereof. Therotor 574 may include a plurality of circumferentially-distributedsuperhard bearing elements (not shown) such as shown and described inrelation to FIGS. 1A-3. In addition, an embodiment of the subterraneandrilling system 500 may include a radial-bearing apparatus (not shown),such as the radial-bearing apparatus 400 of FIG. 5. The radial-bearingapparatus also may include a rotor and a stator, as discussed above.

In operation, drilling fluid may be circulated through the downholedrilling motor 562 to generate torque and rotate the output shaft 556and the rotary drill bit 568 attached thereto so that a borehole may bedrilled. A portion of the drilling fluid may also be used to lubricateopposing bearing surfaces of the stator 572 and the rotor 574 and/or ofthe rotor and stator of the radial-bearing apparatus (not shown). Whenthe rotor 574 is rotated, grooves of the superhard bearing elements ofthe rotor 574 may pump the drilling fluid onto the bearing surfaces ofthe stator 572 and/or the rotor 574, as previously discussed.

Although the bearing assemblies and apparatuses described above havebeen discussed in the context of subterranean drilling systems andapplications, in other embodiments, the bearing assemblies andapparatuses disclosed herein are not limited to such use and may be usedfor many different applications, if desired, without limitation. Thus,such bearing assemblies and apparatuses are not limited for use withsubterranean drilling systems and may be used with various mechanicalsystems, without limitation.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall be open ended and have the samemeaning as the word “comprising” and variants thereof (e.g., “comprise”and “comprises”).

What is claimed is:
 1. A bearing assembly, comprising: a first pluralityof superhard bearing elements distributed about an axis, each of thefirst plurality of superhard bearing elements having a superhardmaterial including a superhard bearing surface, the superhard materialof at least some of the first plurality of superhard bearing elementsexhibiting a maximum thickness that is at least 0.120 inch; and asupport ring structure coupled to the first plurality of superhardbearing elements.
 2. The bearing assembly of claim 1, wherein a distancebetween the superhard bearing surface and the support ring is greaterthan the maximum thickness of superhard material.
 3. The bearingassembly of claim 2, wherein the distance is between about 0.090 inchand about 0.500 inch.
 4. The bearing assembly of claim 2, wherein themaximum thickness of the superhard material is between about 0.100 inchand about 0.312 inch.
 5. The bearing assembly of claim 1, wherein eachof the first plurality of superhard bearing elements includes asubstrate bonded to the superhard material.
 6. The bearing assembly ofclaim 5, wherein each of the first plurality of superhard bearingelements includes a non-planar interface between superhard material andthe substrate.
 7. The bearing assembly of claim 5, wherein each of thefirst plurality of superhard bearing elements includes a steppedinterface between superhard material and the substrate.
 8. The bearingassembly of claim 7, wherein the stepped interface includes a firstsurface and a second surface, and a first thickness of the superhardmaterial on the first surface is substantially less than a secondthickness of the superhard material on the second surface.
 9. Thebearing assembly of claim 8, wherein the first thickness is betweenabout 0.040 inch and about 0.080 inch.
 10. The bearing assembly of claim1, wherein: a portion of a peripheral surface of at least one of thefirst plurality superhard bearing elements is formed by the superhardmaterial; and a surface area of the superhard bearing surface is no morethan 4 times greater than a surface area of the portion of theperipheral surface formed by the superhard material.
 11. The bearingassembly of claim 1, further comprising a second plurality of superhardbearing elements coupled to the support ring structure, the secondplurality of superhard bearing elements having a superhard material thathas a thickness that is less than 0.120 inch.
 12. The bearing assemblyof claim 1, wherein the maximum thickness of the superhard material ofthe first plurality of superhard bearing elements is between about 0.120inch and about 0.312 inch.
 13. The bearing assembly of claim 1, whereinthe superhard bearing surfaces of the first plurality of superhardbearing elements are convex or concave.
 14. A bearing apparatus,comprising: a first bearing assembly including: a first plurality ofsuperhard bearing elements, each of the first plurality of superhardbearing elements including superhard material having a first superhardbearing surface; and a second bearing assembly including: a secondplurality of superhard bearing elements, each of the second plurality ofsuperhard bearing elements including superhard material having a secondsuperhard bearing surface positioned and oriented to slidingly engagethe first superhard bearing surfaces of the first bearing assembly, thesuperhard material of at least some of the second plurality of superhardbearing elements exhibiting a maximum thickness that is at least 0.120inch; and a second support ring structure coupled to the secondplurality of superhard bearing.
 15. The bearing assembly of claim 14,wherein the maximum thickness of the superhard material of the secondplurality of superhard bearing elements is between about 0.120 inch andabout 0.312 inch.
 16. The bearing apparatus of claim 14, furthercomprising a gap between the first support ring structure and the secondsupport ring structure, the gap having a height dimension that isbetween about 0.200 inch and about 1.00 inch.
 17. The bearing apparatusof claim 14, wherein each of the one or more first bearing surfaces andthe second superhard bearing surfaces is substantially planar.
 18. Thebearing apparatus of claim 14, wherein each of the first bearingsurfaces is convex and each of the second bearing surfaces is concave.19. The bearing apparatus of claim 14, wherein the second bearingassembly includes a third plurality of superhard bearing elements thatinclude superhard material that has a thickness that is less than 0.120inch.
 20. The bearing apparatus of claim 14, wherein each of the secondplurality of superhard bearing elements includes a substrate bonded tothe superhard material, and wherein each of the second plurality ofsuperhard bearing elements includes a non-planar interface betweensuperhard material and the substrate.